Subacute combined degeneration

Definition

Alternative Names

Subacute combined degeneration of the spinal cord; SCD

Causes

Subacute combined degeneration is caused by vitamin B12 deficiency. It mainly affects the spinal cord. But its effects on the brain and the peripheral (body) nerves are the reason for the term "combined." At first, the nerve covering (myelin sheath) is damaged. Later, the entire nerve cell is affected.

Doctors do not know exactly how a lack of vitamin B12 damages the nerves. It is possible that the lack of this vitamin causes abnormal fatty acids to form around cells and nerves.

People are at high risk for this condition if vitamin B12 cannot be absorbed from their intestine or if they have:

Exams and Tests

The health care provider will perform a physical exam. The exam usually shows muscle weakness and sensation problems on both sides of the body, especially in the legs. Knee jerk reflexes are often decreased. Muscles may develop spasticity. There may be reduced senses of touch, pain, and temperature.

Mental changes range from mild forgetfulness to severe dementia or psychosis. Severe dementia is uncommon, but in some cases, it is the first symptom of the disorder.

An eye exam may show damage to the optic nerve, a condition called optic neuritis. Signs of nerve inflammation may be seen during a retinal exam. There may also be abnormal pupil responses, decreased visual acuity, and other changes.

Treatment

Early treatment improves the chance of a good outcome.

Vitamin B12 is given, usually by injection into a muscle. Injections are often given once a day for a week, then weekly for about 1 month, and then monthly. Vitamin B12 supplements, either by injection or high-dose pills, must continue throughout life to prevent symptoms from returning.

Outlook (Prognosis)

How well a person does depends on how long they had symptoms before receiving treatment. If treatment is received within a few weeks, complete recovery may be expected. If treatment is delayed for longer than 1 or 2 months, full recovery may not be possible.

Untreated, the disorder results in continued and irreversible damage to the nervous system.

Possible Complications

Complications can include permanent, progressive loss of nerve and mental functions.

When to Contact a Medical Professional

Call your health care provider if abnormal sensations, muscle weakness, or other symptoms of subacute combined degeneration develop. This is particularly important if you or a family member has had pernicious anemia or other risk factors.

Prevention

Some vegetarian diets, especially vegan, may be low in vitamin B12. Taking a supplement can prevent the disorder.

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.